1. Field of the Invention
The present invention relates to installation technique for optical fibers, and in particular to an installation structure having a V-shaped groove for placing an optical fiber.
2. Description of the Related Art
There has been known an installation structure having a V-shaped groove for placing an optical fiber at a predetermined position and a pressing plate covered on the optical fiber to fix it in the V-shaped groove, thereby to position and hold the optical fiber with no adjustment. Accordingly, such an installation structure has been widely employed in the field of a device requiring the installation of an optical fiber with no adjustment, for example, in an optical communication module for optically coupling an optical fiber with a light-emitting device used as a light source, or in an optical connector for optically connecting optical fibers with each other, or the like. As a structure for connecting optical fibers with each other, there has been known a ferrule type connector for connecting the optical fibers through a ferrule mounted on an end outer periphery of both optical fibers.
As techniques relating to an installation structure having a V-shaped groove for placing an optical fiber, there have so far been proposed various types. See xe2x80x9cA method of manufacturing a photoelectric conversion module having an optical fiberxe2x80x9d as described in Japanese Patent Application Laid-open Publication No. 61-105517, xe2x80x9cA method of manufacturing an optically coupled device and an edge-emitting type semiconductorxe2x80x9d as described in Japanese Patent Application Laid-open Publication No. 8-201662, xe2x80x9cAn optically coupled module and a method of manufacturing the samexe2x80x9d as described in Japanese Patent Application Laid-open Publication No. 9-127375, etc.
According to a conventional installation structure having the V-shaped groove, positioning, alignment and fixing of an optical fiber are carried out together in one whole V-shaped groove. Therefore, too much large area is required for contacting the groove surface of the V-shaped groove with the optical fiber, and there has been a risk of an occurrence of a floating or a bending of the optical fiber due to the elasticity of the optical fiber depending on an installation angle, a pressing force and a pressing method at the time of installing the optical fiber.
Because of the above reason, according to the conventional installation structure for an optical fiber, it has been difficult to install a plurality of optical fibers in the same precision on a plurality of V-shaped grooves. In other words, it has been difficult to position optical fibers in alignment in high precision with satisfactory reproducibility.
Particularly, in recent years, there has been an increasing trend of applications requiring an installation of an optical fiber having a lens at the end thereof or a multi-core array optical fiber. There has also been an increasing requirement for installing the optical fiber in much higher precision on the V-shaped groove substrate. However, the prior-art installation structure has not been able to meet sufficiently such requirement for high-precision installation.
In the mean time, for preventing the floating and bending of an optical fiber, it is necessary to fix the whole periphery of the optical fiber. However, according to the prior-art installation structure for an optical fiber, the optical fiber is fixed by being pressed with a pressing plate, that is, the optical fiber is mechanically sandwiched between the pressing plate and the V-shaped groove. Therefore, it is structurally impossible to fix the whole periphery of an optical fiber based on the prior-art installation structure. As a result, according to the prior-art installation structure for an optical fiber, the fixing strength of an optical fiber is not sufficient and there has been a possibility of a deviation or dropping of the optical fiber.
Further, according to the prior-art installation structure for an optical fiber based on a fixing system using a pressing plate, at the time of fixing the pressing plate to the V-shaped groove substrate with a fixing agent such as a resin, a solder or the like, it is not possible to prevent this fixing agent from flowing into the V-shaped groove where the optical fiber is going to be positioned. The flow of the fixing agent into the V-shaped groove possibly causes a floating and a positions deviation of the optical fiber. Therefore, it can be said that the prior-art installation structure for an optical fiber involves factors for further interrupting a high precision installation of the optical fiber.
In Japanese Patent Application Laid-open Publication No. 8-194135, a substrate for fixing an optical fiber has been disclosed with has a V-shaped groove with varying in width along the optical fiber. Such a V-shaped groove allows the optical fiber to be arbitrarily angled to adjust the optical axis or the optical fiber just right. In other words, this fiber fixing substrate needs to adjust the optical axis of the optical fiber. Therefore, this prior art is not related to an installation structure for positioning and holding the optical fiber with no adjustment.
It is an object of the present invention to provide an installation structure for an optical fiber, which enables an optical fiber to be placed on a V-shaped groove with reliability and precision.
It is another object of the present invention to provide an installation structure which can suppress a floating or a bending of the optical fiber due to its elasticity and which enables the whole periphery of the optical fiber to be fixed, for achieving the installation of the optical fiber in high precision, with high strength and with high reliability.
According to the present invention, in an installation structure for positioning and holding an optical fiber by means of a V-shaped groove formed on a substrate, the V-shaped groove comprises a positioning section and an alignment fixing section. The positioning section has a groove width and a groove depth for allowing an outer periphery of the optical fiber to have a contact therewith. The alignment fixing section has a groove width and a groove depth larger than those of the positioning section to an extent for not allowing the outer periphery of the optical fiber to have a contact therewith, when the optical fiber is disposed on the V-shaped groove.
Since the V=shaped groove is divided into the positioning section and the alignment fixing section, the outer peripheral of the optical fiber comes into contact with only the positioning section to place it at a predetermined position and is not in contact with the alignment fixing section. Therefore, it is possible to fix the optical fiber with a fixing agent in the alignment fixing section and to minimize the length of the positioning section.